Production of sulfur from sulfur dioxide obtained from flue gas

A regenerable process for recovery of elemental sulfur from a gas containing sulfur dioxide comprising the steps of:

• (a) contacting said gas with an aqueous, alkaline reaction medium containing sodium sulfite in concentration sufficient so that a slurry containing solid sodium sulfite is formed in step (c), to react sulfur dioxide with sodium sulfite to form a solution containing dissolved sodium pyrosulfite and sodium sulfite;
• (b) separating sulfur dioxide from the solution produced in step (a) to leave a residual mixture containing water, sodium sulfite and a sodium pyrosulfite, the amount of sulfur dioxide separated being equal to about one-third the amount of sulfur dioxide which reacted with sodium sulfite in step (a);
• (c) adding, in substantial absence of air, sufficient water and sodium bicarbonate to the residual mixture formed in step (b) to react with the dissolved sodium pyrsulfite and form a slurry of solid sodium sulfite suspended in the resulting aqueous, alkaline reaction medium and gaseous carbon dioxide;
• (d) separating the gaseous carbon dioxide formed in step (c);
• (e) separating the solid sodium sulfite from the acqueous, alkaline reaction medium and recycling said separated reaction medium to step (a);
• (f) reducing the separated sodium sulfite to sodium sulfide;
• (g) adding the sodium sulfide formed in step (f) to an aqueous reaction medium containing sodium bicarbonate and, in the substantial absence of air, carbonating the resulting mixture with the gaseous carbon dioxide formed in step (c) to form a slurry of solid particles of sodium bicarbonate dispersed in an aqueous reactor medium containing sodium bicarbonate, along with a gas composed primarily of hydrogen sulfide;
• (h) recovering the hydrogen sulfide formed in step (g) and reacting it with the sulfur dioxide separated in step (b) to form elemental sulfur, to be recovered, and water;
• (i) separating from the slurry formed in step (g) an amount of the reaction medium containing sodium bicarbonate equal to the amount added to sodium sulfide in step (g) and recycling said separating reaction medium to step (g);
• and
• (j) recycling to step (c) the sodium bicarbonate formed in step (g).